Electric circuit control



Dec. 3, 1940. A. L. RIGHE ELECTRIC CIRCUIT CONTROL Original Filed Jan. 27, 1936 BMJ Patented Dec. 3, 1940 UNITED STATES PATENT OFFICE ELECTRIC CIRCUIT CONTROL Application January 27, 1936, Serial No. 61,023 Renewed February 3, 1940 8 Claims.

This invention relates to improvements in the arrangement of electrical circuits and especially circuits for lthe control of the fuel supply to heating apparatus, particularly domestic oil burners.

It is an object of this invention to provide a control which permits the automatic operation of an electric motor which supplies fuel to the heating device under the control of a thermostat or hydrostat or by manual means and which automatically cuts oi the source of power from the motor if within a predetermined time after the motor starts normal combustion conditions do not` occur.

While this device is primarily intended for the use described its application is not limited to such use since it may be employed in a wide Variety of circuits and it may be actuated by changes in pressure, temperature, drafts or humidity alone or in combination, or by manual control.

The accompanying sheets of drawings illustrate specific embodiments of the invention as applied to domestic oil burners of the electrically operated and thermostatically controlled type,

but the invention is not limited to these embodiments.

In the drawing: Figs. 1 and 3 are diagrammatic illustrations of the wiring of the controls in two different forms.

Fig. 2 is a top view of the snap spring assembly used in Figs. 1 and 3.

Figs. 4 and 5 are detailed views of one of the elements of Fig. 3.

The system of Fig. 1 includes a motor 18 for operating a liquid fuel burner of a building heating system (burner and heating system not shown). It includes, also, a thermostatic switch 19 responsive to the temperature of the room air a source of electric power (not shown). The

room thermostatic switch -19 may consist of an electric switch of the type shown in United States patent to P. K. McGall 1,960,020, and an expansible liquid filled thermostatic bellows 92A exposed to the air in the room or space to be heated. The circuit through the switch 19 and motor 18 is completed through conductor 8|, insulated conductor 82, resistor 83, insulated conductor 84, fixed contact 85, movable contact 86, tension strip spring element 81 of spring assembly 88, screw stud 89, thermostatic metal blade 90 and conductor 9|. The thermostatic metal blade 90, shown in the room temperature position, is deformed upwardly when heated by resistor 83 which surrounds it but which is separated thereand a knife switch for making connection to from by suitable insulating material such as mica. The blade is mounted in cantilever fashion at 92 and has screw stud 89 mounted at its free end locked in position by nut 93. The spring assembly 88 of the form shown in Fig. 2 comprises an elongated strip spring member 81 operatively mounted on a necked portion of the stud 89 which engages the notched hole 94. The side spring elements 95 are compressively abutted against grooved or notched abutments 96 thereby putting member 81 in tension since the ends of elements 81 and 95 opposite their mounted ends are fastened together to form movable contact 86. The operation of a snapswitch of this general type is described .in Patent No. 1,960,020 except that in the present construction the snap movement of contact 86 is produced by the movement of the mounting point 94 of tension member 81 by stud 89. 20

An abutment 91 with pivoted catch 98 and strip spring 99 mounted thereon, is mounted frictionally in a well-known manner on the end of the shaft 100 operated by the helical thermostatic member of a combustion responsive stack switch 2 (not shown) of the heating system. This stack o switch is located in the smoke iiue of the liquid fuel burner to respond to the heat of combustion thereof. The abutment 91 is in the dotted position when the thermostatic spiral is cold. Upon heating of the cold spiral as a result of the combustion of the oil in the furnace, abutment 91 revolves clockwise to the position shown in full lines, that is, when normal ignition occurs. The passage of current through the circuit described including resistor 83 heats blade 90. As the blade 90 is heated it moves upwardly and the tension center line of the spring 81 crosses the line of the pivoting grooves in abutments 96 causing the spring assembly 88 and especially movable contact 86 to suddenly snap upwardly and break the circuit through resistor 83. In its upward motion the contact 86 moves catch 98 out of its path against the force of spring 99 but is stopped by abutment 91 which is in the full line position as a result of the rotation of the thermostatic spiral as described above. After the passage of the contact 86 the catch 98 again snaps into the position shown in full lines in Fig. 1, and thus prevents return of the contact 86 to its initial position as thermostatic blade 90 moves downwardly again. The catch 98 is electrically connected to abutment 91 whereby the electrical circuit from conductor 9i through blade 90, stud 89 and spring assembly 88 is completed through flexible conductor l0! when contact 86 engages either the catch 98 or the abutment 91. The resistor 83 is thereby disconnected from the circuit and the motor circuit completed by a path of negligible resistance. If, however, normal 5 ignition does not occur the thermostatic spiral does not revolve shaft so that abutment 91 and catch 98 remain in the position indicated by the dotted lines. When the spring assembly 88 snaps over under these conditions as a result of the heating oi' element 83 contact 86 clears catch 98 and abutment 91 and is carried up against stop |02 as shown in dotted lines thus opening the motor circuit. The heater element 83 and blade 90 cool and blade 90 returns to its cold position. The spring assembly 88 does not snap back to its initial position but remains in the position shown by the dotted lines since the tension center line of tension member 81 remains above the operative notches in abutments 96. The motor circuit is therefore held open until plunger |02A is manually depressed whereby the tension center line of member 81 is depressed below the operative notches in abutments 96 and thereby returns the spring 88 to its original position and again closes the motor circuit. Plunger |02A may also operate against tension strip spring 81. Also, if at any time during motor operation and after blade 90 has cooled to normal temperature, the stack temperature fall-s below a predetermined point, the counter-clockwise rotation of abutment 91 carries catch 98 from under the end of contact 86, allowing it to return to its initial position. This completes the circuit through resistor 83 and thermostatic blade 90 is again deformed causing the spring assembly 88 to snap into the upper position thus shutting ofi' the motor. If such rotation of the abutment 91 occurs before blade 90 cools sufllciently to give the contact 86 a downward pressure, assembly 40 88 immediately snaps upward into the upper position as abutment 91 rotates sufficiently to release it. thereby opening the motor circuit. The rotation of abutment 91 in both directions is limited by stop 91A without limiting the movement of 45 shaft |00 because of the frictional slip arrangement between shaft |00 and abutment 91. In Fig. 1 the support Apoint of tension member 81 is raised and lowered by blade 90 with respect to the pivot points of compression members 95 50 on abutment 96 thereby operating spring assembly 88. This same relative movement of the tension member and the compression member pivot points for operating the switch also may be obtained by keeping the tension member sup- 55 port point fixed and attaching the abutment 9k to thermostatic blade 90 whereby the pivot points of the compression strip 95 move in a vertical direction causing the switch to operate when they cross the tension center line of tension strip 81.

Fig. 3, in which the cold condition of the control with the burner not operating is illustrated in solid lines, represents a modification of rny invention shown in Fig. 1, which has the advantage that the motor |03 is stopped if a small drop in 65 temperature occurs in the stack: after ignition has been established and after thermostatic blade |04 has returned to its normal cool position. The spring assembly |05 immediately snaps over to the upper position upon anticlockwise rotation 70 of abutment |06 instead of the movable contact |08 returning to engage the fixed contact |09 and thereby avoiding a continued operation of the motor |03 until the blade |04 is again heated. Upon closure of thermostat switch ||0 current 75 flows from switch Hi through conductor |12,

switch 0, conductor ||3, screw ||4A, blade |04, stud H5, tension spring element H6, contacts |08 and |09, conductor ||1, heating element H8, conductor |25, motor |03 and conductor ||9 to switch Heating element ||8 is inductively wound about thermostatic blade |04, and insulated therefrom by material such as mica. Blade |04 is made of magnetic material and the circulation of current about it in the winding I8 causes a magnetic flux to be set up. This flux is communicated to iron bracket H4, which attracts iron armature |20 which armature is a portion of the element |2| loosely mounted on shaftY |22 attached to the spiral thermostatic element. Since the element |2| is loosely mounted on the shaft |22 and is free to turn about the axis of that shaft, the attraction between armature |20 and the bracket 4 causes a movement of armature |20 against the force of a retractile spring |23 until the position shown in Fig. 4 is assumed, or until the element 2| stops against the abutment |26. In the position of Fig. 4, iron armature |20 has stopped against the insulator ||4b on the projection ||4. The abutment |06 is attached to the shaft |22 frictionally in a well-known manner and when the stack temperature rises, due to the establishment of combustion, the abutment |06 is turned clockwise from the pf on shown in full line in Fig. 3 to that showt.; n dotted line, and carries the element |2| and he armature. 20 into the position shown in dotted line in Fig. 3. Heating of blade |04 by element |8 causes it to be deformed upwardly and to carry with it the mounting of the tension spring element ||6 causing the movable contact |08 to snap upwardly as previously described out of engagement with the xed contact |09, and against the abutment |06. This action leaves the motor operating current passing through only the right half of the heating element ||8 as it flows from contact |08 through abutment |06. conductor |24, a portion of heating element |8 to conductor |25. This causes thermostatic element |04 to remain heated suiiiciently to hold contact |08 in engagement with abutment |06 during the period of motor operation. If, during the time thermostat switch ||0 is closed, combustion fails While the motor |03 is in operation and the stack temperature falls, abutment |06 is moved in a counter-clockwise direction. carrying its lower point to the right out of the nath of travel of the contact |08. The element |2| follows it into the position shown in Fig. 4 and contact 08 is free to snap into its upper position as shown in dotted line in Fig. 3. This opens the motor circuit and blade |04 cools until the entire spring assembly |05 takes the position shown in dotted line in Fig. 3. The motor circuit can be reclosed only by the manual operation of the plunger |26, which can be made to force the blade |04 or tension member 6 downward and carry the tension center line of spring element ||6 across the operative mounting line of compression element |21 causing the entire spring assembly |05 to snap back into its full line or cold position.

When thermostat switch ||0' opens and a normal shutdown of the burner occurs, abutment 06 rotates into the position shown in full line in Fig. 3 but the element |2| does not follow it since iron bracket ||4 is demagnetized. Spring |23 causes armature |20 and the element |2| to assume the position shown in full line in Fig. 3.

. Contact |08 is thus prevented from snapping into its upper position as indicated in dotted line and when blade |04 has cooled contact |08 snaps into engagement with contact N9 and the device is ready for another normal cycle of motor operations. The rotation of abutment |06 in both directions is limited by stop 106A without limiting the movement of shaft |22 because of the frictional slip arrangement between shaft |22 and abutment |06.

It will be apparent to those skilled in the art that the specific embodiments of the invention herein shown and described are offered merely by way of example and that the invention is capable of many modifications and variations. Accordingly, the invention is to be limited only in accordance with the appended claims.

I claim:

1. The combination with a heating device of a burner, a motor for operating said burner, a resistance heating element, an electric power supply for said motor and said heating element, a metallic thermostatic strip member mounted at one end and free to move at the other, said resistance heating element being adjacent said thermostatic strip member, and a multiple-position snapswitc'h comprising the combination of an elongated tension strip operatively mounted at the free end of said thermostatic strip member with the other end free to move. adjacent compression spring means of shorter effective length with an end thereof connected to the free end of said tension strip and stops comprising electric contacts between which said connected end portion moves, the opposite end of said spring means being pivoted at such a point laterally adjacent said tension strip that said spring means are in longitudinal compression, said mounting point of said tension strip being movable by said thermostatic strip across the plane of said compression spring means pivot point, one of said stops for said connected end portion being under the influence of combustion conditions of said burner, an electric circuit connecting said power supply, said motor, said resistance heating element, and the contacts of said switch. said switch and said circuit being so constructed and arranged that when said switch is in one position against one of said stops said electric power supply is connected with both said motor and said resistance element. and when said connected end portion of said switch is in contact with the stop which is under the influence of combustion conditions of said burner said motor remains connected to said power supply and said resistance element is disconnected therefrom, and when a predetermined temperature is developed in said resistance element and said combustion-influenced stop is not subjected to combustion conditions said connected end portion snaps into a position out of contact with both of said stops and disconnects both said motor and said resistance element from said power supply.

2. In combination in a device of the class described, a spring toggle snap mechanism including a bimetalllc thermal actuator and an electric contact making follower, a first fixed stop for said follower, said first fixed stop constituting an electric contact, a second fixed stop for said follower, a removable stop for said follower, said removable stop constituting an electric contact and being movable into and out of operative position, an electric heater for said thermal actuator, said heater being connected between said first fixed stop and said removable stop, said removable stop and said follower being connected in an electric circuit to control it, said follower being so constructed as to snap from the position of the first xed stop to that of the removable stop in response to movement of said actuator when warmed by said heater, and to snap from the position of the removable stop to that of the first fixed stop in response to a return movement of said actuator upon normal cooling thereof, said follower requiring, in order to snap away from the third fixed stop, a movement of said actuator through a distance in excess of that4 resulting from said normal cooling thereof, said actuator being movable manually through said excess distance, whereby, (1) when said follower engages said rst fixed stop said heater is connected in the circuit to be controlled, (2) when said follower engages said removable contact said circuit is closed but excludes said heater, and (3) when said follower engages said second fixed stop said circuit is open.

3. The combination of the immediately preceding claim wherein said removable stop includes a catch so constructed and arranged that it retains said follower next said removable stop when said removable stop is in operative position, said catch being constructed and arranged to release said follower in response to said removable stop movingout of operative position.

4. In combination with an electric machine, a resistance element, an electric power supply for said electric machine and said resistance element, a combustion device, an automatic multiple-position switch having three operated positions thereof, an electric circuit connecting said power supply, electric machine, resistance element and switch, said switch and said circuit being so constructed and arranged that said switch in its initial position connects both said electric machine and said resistance element to said power supply, Ameans operable in response to heating of said resistance element to operate said switch out of the initial position thereof to disconnect simultaneously said resistance element and said electric machine from said power supply, an electric contact movable into the path of the movable element of said switch to restrict the movement thereof, said electric contact being so connected in said electric circuit as to provide an electrical connection of said power supply with said electric machine Without including said resistance element, means operable upon establishment of combustion to introduce said electric contact into the path of said movable element of said switch, said movable element and said electric contact being so constructed and arranged that said movable contact moves unrestricted from its initial position beyond said electrical contact to open circuit position should said combustion responsive means fail to move said contact into position to restrict the movement of said movable element.

5. In combination, an electric machine, a spring snap switch including a thermal actuator and a snap follower, a pair of fixed stops for said follower. a removable stop for said snap follower movable into and out of operative position, an electric heater for heating said thermal actuator, an electric power supply, circuit connections between said power supply. said heater, said electric machine and said switch, said follower being so constructed that it snaps back and forth between the position of the first fixed stop and the operative position of the movable stop in response to the heating and cooling of said thermal actuator, said follower.' being so con l structed that it snaps away from the second new,

stop only in response Ato an excursion of said actuator greater than that required to cause said follower to snap between said rst fixed stop and the operative position of said removable stop, and control means for moving said removable stop into and out of operative position, said snap switch including contacts operated by said ollower, said switch and said circuit being so constructed and arranged that said switch controls said heater, and, through its control of said heater, causes itself to operate out of the position of said rst fixed stop.

6. The combination of the immediately preceding claim wherein said removable stop includes a catch so constructed and arranged that it retains said follower next said removable stop when said removable stop is in operative position, said catch being constructed and arranged to release said follower in response to said removable stop moving out of operative position.

7. The combination of an electric machine, a resistance element, an electric power supply for said resistance element, a three position switch having moving and stationary contacts, and having a normal position and two operated positions for a moving contact, said switch including a thermal actuator operating under the heating Ainfluence of said resistor element to move said moving contact between said normal position and the rst of said operated positions and into the second of said operated positions, said thermal actuator being so constructed that it tends to move said moving contact into said normal position when said resistance element is deenergized, and circuit connections between said switch, power supply, and resistance element (1) for energizing said resistance element and electric machine when said moving contact is in said normal position, (2) for energizing only said electric machine when said moving contact is in said rst operated position, and (3) for deenergizing both said resistance element and electric machine when said moving contact is in said second operated position, and control means operable to determine whether said switch, when operating said moving contact out of said normal position, moves said contact into said rst operated position or into said second operated position.

8. In combination, an electrical device, a snap acting thermostat having a thermal element heated by said electrical device and having also a snap-acting electric contact operable to snap into a rst extreme posi-tion in response to a temperature change of said thermal element, and to snap from said rst extreme position toward a second extreme position in response to an opposite temperature change, a movable obstruction movable into obstructing position to stop said snap-acting contact in an intermediate position and thereby prevent it from moving into said second extreme position and movable therefrom into contact freeing position to release said snapacting contact for snapping beyond said obstruction into said second extreme position, and another electric contact cooperating with said movable contact for controlling the energization of said electrical device.

ARTHUR LEWIS RICHE. 

